Forces Circular Motion Chapter 9 3 9 4

Forces & Circular Motion Chapter 9. 3 -9. 4

Forces & Circular Motion • Centripetal force • Centrifugal force • Newton’s 3 rd Law states for every action there is an equal and opposite reaction…centripetal and centrifugal forces are the opposite and equal forces that act on objects that are moving along a circular path.

Centripetal Force • Any force that causes an object to follow a circular path • “center seeking” force • Without this force, the motion would be along a straight line

• If you whirl a can over your head attached to a string, you provide the centripetal force in order to keep the can revolving in a circle around you.

• When a car rounds a corner, the sideways acting friction between the road and the tires provides the centripetal force that holds a car in a curved path.

Centrifugal Force • The outward force of an object moving in a circular motion • “Center fleeing” force – Outward force

• If you are riding in a car without a seatbelt and the car suddenly stops you fly forward. Why? – because of the absence of a force (which the seatbelt provides) • Which type of force does the seat belt apply: centripetal or centrifugal?

• The seatbelt provides a centripetal force…just because you fly forward doesn’t mean that a centrifugal force is acting on you.

• What would happen if the string breaks?

• The can would travel in a straight line (tangential speed), not because there is no centrifugal force but because there is no longer a centripetal force acting on the can to keep it moving in a circular path.